A conventional non-contact type position sensor of this type is disclosed, for example, in Japanese Laid-open Patent No. H2-240585.
The conventional non-contact type position sensor is described hereinafter by referring to the drawings.
FIG. 6 is a perspective exploded view of the conventional non-contact type position sensor. FIG. 7 is a side sectional view of the conventional non-contact type position sensor. The non-contact type position sensor is used, for example, for detection of a crank angle in an ignition timing control device of an internal-combustion engine.
In FIG. 6 and FIG. 7, magnet 1 has N pole and S pole. First magnetic element 2 has magnet 1 fixed thereon and has one end 2A bent to project upward to magnet 1 side. Second magnetic element 3 of an inverted L-shape has one end 3A bent in one direction. This one end 3A is disposed at a position facing one end 2A of first magnetic element 2.
Magnetic detecting element 4 is disposed at a position facing magnet 1 at the side of second magnetic element 3. Case 5 made of resin accommodates magnet 1, first magnetic element 2, second magnetic element 3, and magnetic detecting element 4 in the inside thereof, and has opening 5A. Case 5 also has connector 6. Connector 6 has an integrally formed connector terminal 7. Connector element 7 has one end in the inside of case 5, and the other end projecting outward. One end of connector terminal 7 in case 5 is electrically connected to lead terminal 8 lead out from magnetic detecting element 4. Lid 9 made of resin closes opening 5A of case 5.
In the conventional non-contact type position sensor having a configuration above-explained, the operation thereof is described below.
In the conventional non-contact type position sensor described above, one end 2A of first magnetic element 2 and one end 3A of second magnetic element 3 face each other across a gap. Magnet 1 and magnetic detecting element 4 are also facing each other across a gap.
Magnetic flux shutter 10B as shown in FIG. 8A and FIG. 8B is inserted into this gap. Magnetic flux shutter 10B is mounted on rotary shaft 10A of the object in the vertical direction, and rotates together with rotary shaft 10A of the object. As magnetic flux shutter 10B moves in the radial direction, the magnetic flux density of magnet 1 reaching magnetic detecting element 4 changes. Magnetic detecting element 4 outputs this change of the magnetic flux density as an output signal. This output signal is input into a computer or the like (not shown) by way of lead terminal 8 and connector terminal 7 in connector 6. Thus, the rotational angle of rotary shaft 10A of the object is detected.
In the conventional configuration above-explained, magnetic flux shutter 10B rotates while being inserted between magnet 1 and magnetic detecting element 4. Therefore, in magnetic force shutter 10B, an electromagnetic induction is caused by the magnetic flux of magnet 1. As a result, as shown in FIG. 8A, when magnetic flux shutter 10B rotates in an positive direction, magnetic force shutter 10B appears to be magnetically charged as the N pole. To the contrary, when magnetic force shutter 10B rotates in the reverse direction, as shown in FIG. 8B, magnetic force shutter 10B appears to be magnetically charged as the S pole. Accordingly, depending on the rotating direction of the magnetic force shutter 10B, the magnetic flux applied to magnetic detecting element 4 varies. Therefore, the output varies between the normal rotation and reverse rotation of rotary shaft 10A of the object. Hence, hysteresis occurs in the output characteristic of the non-contact type position sensor.